1. Field of the Invention
The present invention relates to a process for growing a multielement compound single crystal. It relates more particularly to a process for growing a ternary compound semiconductor single crystal, e.g., indium gallium antimonide (In, Ga)Sb, indium gallium phosphide (In, Ga)P, indium gallium arsenide (In, Ga)As or indium arsenic phosphide In(As, P), or an oxide single crystal, e.g., .beta.-barium diboron tetroxide .beta.-BaB.sub.2 O.sub.4, dilithium tetraboron heptoxide Li.sub.2 B.sub.4 O.sub.7 or lithium triboron pentoxide LiB.sub.3 O.sub.5.
2. Description of the Related Art
Since material values, such as lattice constants and forbidden energy band width, of a multielement compound single crystal can be selected by means of changing composition ratios of elements of the multielement compound single crystal, the multielement compound single crystal is now attracting attention as a substrate for epitaxy.
In growing the multielement compound single crystal, the concentration of an element of a high segregation coefficient in a melt of a raw material, however, decreases, so that a bulk multielement compound single crystal of a uniform composition cannot be grown. For example, indium gallium arsenide (In, Ga)As was grown by the liquid encapsulated Czochralski method and has been reported (Paper Presented by W. A. Bonner et al., of 6th Conf. on Semi-insulating 3-5 Materials, Toronto, Canada, Chapter 3, PP. 199-204, 1990). This example does not present a single crystal of a uniform composition along the growth axis of the single crystal.
In addition, a process has been reported which comprises the steps of growing indium gallium antimonide of a uniform composition and concurrently feeding a volume of a solute to cancel a variation in the composition of a melt of a raw material. The solute is fed from a solute container mounted on the underside of a crucible through the bottom of the crucible. This is a single crystal growth process in which the liquid encapsulated Czochralski method and the solute feed control method are combined (Research Report of Sizuoka University, Electronic Engineering Institute, vol.20, PP. 193-197, 1985 and Japanese Unexamined Patent Application Publication SHO.62-3097). This process has drawbacks since it is difficult to control the dissolution rate of the solute in the melt, it is difficult to control the composition of the melt during growth of the single crystal, and it is impossible to stably grow the single crystal of a uniform composition.
In growing the single crystals of ternary oxides, e.g., potassium titanium oxide phosphate KTiOPO.sub.4, .beta.-barium diboron tetroxide .beta.-BaB.sub.2 O.sub.4, dilithium tetraboron heptoxide Li.sub.2 B.sub.4 O.sub.7 and lithium triboron pentoxide LiB.sub.3 O.sub.5, the flux method is usually employed. However, the flux method has a drawback in that the composition of a melt of a raw material varies as the single crystal is grown.